We have undertaken projects aimed at the isolation and characterization of three types of plasmodial genes: 1) genes involved in the acquisition of drug resistance by the parasite 2) genes that code for antigenic surface protein of the parasite 3) genes that code for the stable RNAs (ribosomal RNA, 5.8S RNA, 5S RNA and transfer RNA). Characterization of both pyrimethamine sensitive and pyrimethamine resistant parasites indicates that amplification of the dihydrofolate reductase gene is involved in the acquisition of drug resistance. The genes for ribosomal RNA, 5.8S and 5S RNA have been characterized by DNA restriction analysis. There are only four ribosomal genes in plasmodium. When these are compared by E M techniques, they are found to have large differences in primary sequence. The translation of these genes could lead to the presence of varying types of ribosomes. Finally a new immunoscreening technique has been developed to isolate antigenic proteins from plasmodium.